On May 13, OpenAP launched a standardized cross-publisher Conversion API (CAPI) backed by nine of the largest U.S. TV and streaming publishers: A+E Global Media, AMC Networks, Fox, Hallmark Media, NBCUniversal, Paramount, Scripps Networks, TelevisaUnivision, and Warner Bros. Discovery.
In a year where every walled garden is moving the ball forward on agent-driven measurement and conversion attribution, this is the most consequential publisher-side counter-move of 2026 so far.
01What CAPI actually does — and why a cross-publisher one is different
A Conversion API is the back-end pipe that sits between an advertiser’s first-party data (purchases, sign-ups, in-app events) and the platform serving the ad. CAPI lets advertisers measure outcomes more reliably than cookie-based pixels, and it bypasses many of the breakage points that erode attribution in browser environments.
Meta has had a CAPI for years. So has TikTok, Pinterest, Snap, Reddit, and most major platforms. What none of them has built is a CAPI that resolves campaign exposure consistently across multiple unaffiliated publishers at once.
That is what OpenAP just built. An advertiser running a campaign across NBCU, Paramount, and WBD can now see exposure de-duplicated across all three and tied to outcomes through a single integration — rather than three separate pixels and three separate attribution models.
02Why this matters for the broader publisher market
| Walled-garden parity, finally | Buyers' biggest measurement complaint about premium publishers has been the integration cost. Three publishers = three integrations = three attribution windows. The Big Nine CAPI compresses that to one. |
|---|---|
| Performance dollars get a credible TV pitch | In a year where every upfront pitch was about "performance" (Disney Compass, NBCU Performance Insights Hub, WBD's outcomes dashboards, YouTube Brandcast, Netflix's Amazon-DSP integration), CAPI is the plumbing that makes those pitches concrete. |
| It sets a floor for what large publishers must offer | If you operate at premium scale and you're not on this CAPI roster, you have a sales-team problem. |
| Independent and mid-tier publishers are now on the wrong side of an attribution moat | A buyer can resolve outcomes across nine premium TV publishers with one integration; doing the same across, say, six independent CTV apps still requires six pixels. Smaller publishers should expect tougher budget allocations until they can plug into a comparable framework. |
03The strategic context: this is OpenAP doing what it was built to do
OpenAP started life as a cross-publisher audience-targeting joint venture. The CAPI launch extends that thesis — shared infrastructure across competing publishers, because the alternative is each of them losing budget to walled gardens individually.
The unspoken subtext: this is also a hedge against agentic buying. When an AI agent allocates a budget across publishers, the publisher that returns clean, structured, comparable outcome signals will win the next campaign. The Big Nine know this. CAPI is the mechanism.
For years the open web's biggest measurement problem has been fragmentation.
04Why this matters
- Your buyers are about to expect this. Once CAPI is live and resolving cross-publisher attribution for these nine, the same buyers will start asking smaller publishers, “what’s your CAPI roadmap?”
- Independent CTV publishers should explore joining or building a parallel framework. OpenAP membership matters; if you can’t join, look at TVData partners, Comscore CTV+, or building a vendor-mediated CAPI through your existing measurement partner (Innovid, Comscore, VideoAmp, iSpot).
- Digital-only publishers should still pay attention. The CAPI standard will likely extend to digital video and display. Get ahead of the integration work now while the standard is forming.
05What publishers should do this quarter
06What marketers should do
07The bottom line
For years the open web’s biggest measurement problem has been fragmentation. The Big Nine CAPI is the first credible cross-publisher response — and it’s the first time in a long time that “premium TV publishers” looks like a measurement category, not just a sales category. Publishers who are part of (or aligned with) this infrastructure will keep their share of the next wave of performance budgets. Publishers who aren’t will need to compete on something else.